Gen III tranny options?

HP2 said
Plan is to attend the Swedish version of Street Week, so drag racing -YES SIR! Hoping to get into high 6's. I don't know if you can call it serious drag racing though.
What's the big difference from the A518 46RH I already have?

I would run what you have already, then. Can be built stronger. The 518 is a 4 speed, the 545 is a 5 speed.